I can't believe I ate the whole thing.

The line is best known as a catchphrase from American television advertising in the late 20th century, associated with Alka-Seltzer’s “Plop, plop, fizz, fizz” campaign. It was typically delivered as a humorous, regretful afterthought by an overindulgent eater—often a man slumped in discomfort—implying he has eaten far more than intended and now needs indigestion relief. Because it circulated widely as a commercial tagline and entered popular speech, it is frequently misattributed as “Anonymous” rather than credited to the advertising campaign and its writers/performers.

On its face, the sentence expresses comic disbelief at one’s own excess: the speaker has finished an entire portion (often implied to be large) and only afterward recognizes the consequences. Its humor comes from the mismatch between the certainty of the evidence (“the whole thing” is gone) and the speaker’s incredulity, suggesting mindless consumption or a lapse in self-control. In popular usage, the phrase became a shorthand for overindulgence and immediate regret—invoked not only about food, but also about any situation where someone goes “too far” before realizing it.

“I can’t believe I ate the whole thing.”
“I can’t believe I ate the whole thing….”
“I can’t believe I ate the whole thing!”